Problem: $ { {-2} \times \left[\begin{array}{rr}{-1} & {3} \\ {2} & {4}\end{array}\right] = {?} } $
Answer: To multiply a matrix by a number, multiply each item of the matrix by the number. ${\left[\begin{array}{rr}{-2}\times{-1} & {-2}\times{3} \\ {-2}\times{2} & {-2}\times{4}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rr}{2} & {-6} \\ {-4} & {-8}\end{array}\right]}$